And then why don't I find a large glass jar filled with live wriggling cockroaches and compete with my coworkers to see how many of them I can swallow whole?

SNMP is awful. SNMP implementations are scarier than web apps (though admittedly not as scary as SSH logins). SNMP is harder to secure. It would be much harder for customers to provide their own trusted implementation of SNMP. I could go on.

There's what SNMP was built for, and then what it actually does.

I've been (un)fortunate enough to implement it more than once. Only a certain class of clients demand it because they already have built a big SNMP infrastructure.